In the related art, a coated tool in which a Ti—Al-based or Cr—Al-based complex nitride layer is coated as a hard coating layer on a surface of a tool body that is formed of a tungsten carbide (hereinafter, referred to as WC)-based cemented carbide, titanium carbonitride (hereinafter, referred to as TiCN)-based cermet, or a cubic crystal boron nitride (hereinafter, referred to as cBN)-based ultra-high-pressure sintered body (hereinafter, collectively referred to as a tool body) by a physical vapor deposition method is typically known, and it is known that this exhibits excellent wear resistance.
However, since the coated tool in the related art, in which the Ti—Al-based or Cr—Al-based complex nitride layer is coated, has relatively excellent wear resistance while abnormal wear such as chipping tends to occur in a case in which the coated tool is used under high-speed intermittent cutting conditions, various suggestions have been made to improve the hard coating layer.
For example, Japanese Unexamined Publication No. 2012-20391 discloses a surface-coated cutting tool that can obtain excellent wear resistance and fracture resistance by a configuration in which a hard coating layer is formed on a surface of a tool body, in which the hard coating layer is formed of one layer or a plurality of layers, T1<T2 is satisfied where T1 represents the thickness of the thinnest portion of the hard coating layer at a ridge line portion of a cutting edge, and T2 represents the thickness at a location of 1 mm away from the ridge line of the cutting edge in a rake face direction, Da and Db are inside specific numerical ranges where a represents a location that is a distance Da in the rake face direction from the ridge line of the cutting edge on the surface of the hard coating layer, and b represents a location that is a distance Db in a flank face direction therefrom, and unevenness in a crystal orientation of crystal grains that form the hard coating layer is equal to or greater than 5 degrees and less than 10 degrees in a region corresponding to 10% or more of a region E that occupies the thickness 0.1T1 to 0.9T1 from the surface of the hard coating layer from the location a to the location b.
In addition, Japanese Unexamined Publication No. 2000-144376 discloses that a film with excellent wear resistance, seizure resistance, and oxidation resistance, with a low friction coefficient, and excellent sliding properties is obtained by forming a complex hard film that is formed of at least two kinds of metal nitride from among nitrides of Cr, Ti, Al, and V on the surface of a tool body and setting an intensity ratio I(111)/I(200) between X-ray diffraction peaks I(111) and I(200) of a (111) plane and a (200) plane that are obtained by X-ray diffraction for the hard film to be a value from 3 to 6.
However, there is a disclosure that TiAlN is deposited as the hard coating layer in the aforementioned coated tool while there is neither disclosure nor indication that the content ratio x of Al is set to be equal to or greater than 0.65.
From such a viewpoint, a technology of increasing the content ratio x of Al to about 0.9 by forming the hard coating layer by a chemical vapor deposition method has also been proposed.
For example, Japanese Unexamined Publication No. 2011-516722 describes that it is possible to deposit a (Ti1-xAlx)N layer in which the value of the content ratio x of Al ranges from 0.65 to 0.95 by performing chemical vapor deposition within a temperature range of 650 to 900° C. in mixed reaction gas of TiCl4, AlCl3, and NH3. However, since an Al2O3 layer is further applied onto the (Ti1-xAlx)N layer for the purpose of enhancing a thermal insulation effect, it is not obvious in this document how the formation of the (Ti1-xAlx)N layer in which the value of the content ratio x of Al is increased up to 0.65 to 0.95 affects cutting performance.
In addition, Japanese Unexamined Publication No. 2011-513594, for example, proposes that heat resistance and fatigue strength of a coated tool are improved by coating, as an outer layer, a (Ti1-xAlx)N layer (where an atomic ratio of x ranges from 0.65 to 0.90) with a cubic structure or a hexagonal structure by a chemical vapor deposition method on a TiCN layer and an Al2O3 layer that are inner layers and applying compressive stress of 100 to 1100 MPa to the outer layer.
For example, Japanese Unexamined Publication No. 2006-82207 discloses a surface-coated cutting tool that includes a tool body and a hard coating layer formed on the body thereof, in which wear resistance and oxidation resistance of the hard coating layer are significantly improved due to either or both Al and Cr elements, at least one kind of element selected from a group consisting of Group 4a elements, Group 5a elements, and Group 6a elements in the periodic table and Si, a compound that is formed from at least one kind of element selected from a group consisting of carbon, nitrogen, oxygen, and boron, and chlorine being contained.
For example, Japanese Unexamined Publication No. 2014-208394 proposes that the adhesion strength between a lower layer and an upper layer may be improved, and chipping resistance and wear resistance may thus be improved by providing a hard coating layer that is formed of the lower layer, an intermediate layer, and an upper layer on a surface of a tool body such that the lower layer has a predetermined average layer thickness and is formed of a TiAl compound that has a cubic structure formed of one layer or two or more layers from among a Ti1-xAlxN layer, a Ti1-xAlxC layer, and a Ti1-xAlxCN layer (X is the content ratio (atomic ratio) of Al and satisfies 0.65≤X≤0.95), the intermediate layer has a predetermined average layer thickness and is formed of a CrAl compound that has a cubic structure formed of one layer or two or more layers from among a Cr1-YAlYN layer, a Cr1-YAlYC layer, and a Cr1-YAlYCN layer (Y is the content ratio (atomic ratio) of Al and satisfies 0.60≤Y≤0.90), and upper layer is formed of Al2O3 that has a predetermined average layer thickness, in order to improve the chipping resistance and the wear resistance in a high-speed intermittent cutting of stainless steel, a Ti alloy, or the like.
In addition, Japanese Unexamined Publication No. 2014-198362 proposes that the adhesion strength between a lower layer and an upper layer may be improved, and the upper layer be formed of an Al2O3 layer that has fine pores with a predetermined pore diameter and pore density to alleviate mechanical and thermal impacts, thereby improving chipping resistance and wear resistance, by providing a hard coating layer that is formed of the lower layer, an intermediate layer, and the upper layer on a surface of a tool body such that the lower layer is formed of a Ti compound that has a cubic crystal structure formed of one layer or two or more layers from among a Ti1-xAlxN layer, a Ti1-xAlxC layer, and a Ti1-xAlxCN layer (X is an atomic ratio that indicates a content portion of Al and satisfies 0.65≤X≤0.95) with a predetermined average layer thickness per layer, the intermediate layer is formed of a Cr compound that has a cubic crystal structure formed of one layer or two or more layers from among a Cr1-YAlYN layer, a Cr1-YAlYC layer, and a Cr1-YAlYCN layer (Y is an atomic ratio that indicates the content ratio of Al and satisfies 0.60≤Y≤0.90), and the upper layer is formed of Al2O3 that has fine pores with a predetermined pore diameter and pore density and an average layer thickness, in order to improve the chipping resistance and the wear resistance in a high-speed intermittent cutting of a heat-resistant alloy such as precipitation hardening stainless steel and an Inconel alloy.
Further, Japanese Unexamined Publication No. 2009-56539 proposes that the high-temperature strength of an (Al1-XCrX)N layer may be improved, and fracture resistance of a hard coating layer in a heavy-duty cutting may thus be improved by providing the hard coating layer formed of the (Al1-XCrX)N layer (where X is an atomic ratio and satisfies X=0.3 to 0.6) on the surface of the tool body, and forming a crystal orientation and a constituent atom shared lattice point distribution form such that in an inclined angle frequency distribution graph created by measuring inclined angles formed by normal lines of {100} planes with respect to a normal line of a polished surface as a surface of the tool body, the highest peak is present in an inclined angle section from 30 to 40 degrees and the total frequencies thereof accounts for equal to or greater than 60% with respect to the entire frequencies, and in a constituent atom shared lattice point distribution graph created by measuring inclined angles formed by normal lines of {112} planes with respect to the normal line of the polished surface as a surface, the highest peak is present at Σ3, and the distribution ratio thereof is equal to or greater than 50% with respect to the entire frequencies, in order to enhance fracture resistance of the hard coating layer in heavy-duty cutting of steel or cast iron, in which a large load acts on the cutting edge.